期刊
ASTROPHYSICAL JOURNAL
卷 928, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4357/ac54ad
关键词
Galaxy abundances; Galaxy disks; Red giant stars; Galaxy structure
资金
- NASA through the NASA Hubble Fellowship [HF2-51434]
- Space Telescope Science Institute [NAS5-26555]
- Alfred P. Sloan Foundation
- U.S. Department of Energy Office of Science
- Center for High Performance Computing at the University of Utah
- Carnegie Institution for Science
- Chilean Participation Group
- French Participation Group
- Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo
- Korean Participation Group
- Lawrence Berkeley National Laboratory
- Max-Planck-Institut fur Extraterrestrische Physik (MPE)
- New Mexico State University, New York University, University of Notre Dame, Observatario Nacional/MCTI
- Shanghai Astronomical Observatory
- Universidad Nacional Autonoma de Mexico
- Yale University
In order to understand the formation of the Milky Way's prominent bar, it is necessary to study whether the stars in the bar have different chemical element compositions compared to the stars in the disk. A new self-calibration approach is developed in this study to eliminate modeling and astrophysical abundance systematics among red giant branch (RGB) stars. The results indicate that there are no abundance variations that match the geometry of the bar and that the mean abundance gradients vary smoothly and monotonically with galactocentric radius.
To understand the formation of the Milky Way's prominent bar it is important to know whether stars in the bar differ in the chemical element composition of their birth material as compared to disk stars. This requires stellar abundance measurements for large samples across the Milky Way's body. Such samples, e.g., luminous red giant stars observed by the Sloan Digital Sky Survey's APOGEE survey, will inevitably span a range of stellar parameters; as a consequence, both modeling imperfections and stellar evolution may preclude consistent and precise estimates of their chemical composition at a level of purported bar signatures, which has left current analyses of a chemically distinct bar inconclusive. Here, we develop a new self-calibration approach to eliminate both modeling and astrophysical abundance systematics among red giant branch (RGB) stars of different luminosities (and hence surface gravity log g). We apply our method to 48,853 luminous APOGEE Data Release 16 RGB stars to construct spatial abundance maps of 20 chemical elements near the Milky Way's mid-plane, covering galactocentric radii of 0 kpc < R-GC < 20 kpc. Our results indicate that there are no abundance variations whose geometry matches that of the bar, and that the mean abundance gradients vary smoothly and monotonically with galactocentric radius. We confirm that the high-alpha disk is chemically homogeneous, without spatial gradients. Furthermore, we present the most precise [Fe/H] versus R-GC gradient to date with a slope of - 0.057 +/- 0.001 dex kpc(-1) out to approximately 15 kpc.
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